1. Field of the Invention
The present invention relates to a technique to generate a character image in which multiple characters, including a player character, a three-dimensional character drawn by three-dimensional polygon data and a two-dimensional character drawn by two-dimensional sprite data, are drawn in a virtual three-dimensional space, the character image being used for displaying a conversation field in which the player character is allowed to have a conversation with other character.
2. Description of the Related Art
When characters including three-dimensional objects are drawn in a virtual three-dimensional space in a personal computer, a video game machine or the like, the three-dimensional objects are generally drawn by three-dimensional polygon data. The three-dimensional polygon data are respectively generated by executing polygon calculations in accordance with a distance between each of the three-dimensional objects in a field of view of a virtual camera and a viewpoint position of the virtual camera or the like.
Further, in various kinds of so-called role playing games (RPG; that is, a video game in which a player plays a role of a character in a world of the video game, and accomplishes a predetermined object while enjoying a process that the character grows through various experiences, a conversation field in which the player character executes an action, such as information gathering by obtaining information by means of inquiry and purchase of items, by having a conversation with other characters in the RPG is generally provided.
It is desired that a large number of characters corresponding to the information obtained by inquiry appear in the conversation field. For this reason, for example, the conversation field may be set to a place such as a market and an open space where a lot of characters (people) gather.
In this regard, in order to reduce the processing load of hardware without omitting objects to be displayed on the virtual three-dimensional space, there is a known process in which all objects are not drawn by three-dimensional polygon data when a lot of objects are to be displayed on the virtual three-dimensional space. Some of the objects that are apart from the viewpoint position of the virtual camera by a predetermined distance or more are drawn by two-dimensional sprite data (for example, see Japanese Patent Application Publication No. 2003-141560).
As described above, a lot of characters are displayed in the conversation field. As the number of three-dimensional objects drawn in the virtual three-dimensional space becomes larger, the amount of polygon calculations increases. Thus, there is a fear that throughput exceeds computing power of hardware such as a personal computer and a video game machine in the case where a large number of three-dimensional objects are to be drawn in the virtual three-dimensional space. In the case where such throughput exceeds the computing power, negative effects such as reduced display speed and screen flicker may occur. Therefore, since the number of characters that can be displayed in one scene, there is a problem that realism (realistic sensation) may be lost in the RPG.
Further, it is thought that a part of objects that is apart from the viewpoint position of the virtual camera by the predetermined distance or more is drawn by two-dimensional sprite data as the patent document mentioned above. However, in the case where a crowded place such as a market and an open space is set to a conversation field, a lot of characters must be drawn even in a place that is not apart from the viewpoint position of the virtual camera by the predetermined distance or more. Thus, there is a problem that realism (realistic sensation) may be lost in the RPG.